1. Field of the Invention
This invention relates generally to manually driven brushes and, specifically, to improvements in manually driven, rotary brush toothbrushes or similar apparatus.
2. Discussion of the Relevant Art
Over the past three decades, dental prophylaxis, in the form of regular brushing with decay-preventing dentifrices, has served to improve the nation's dental and general health to a significant degree. Notwithstanding the advances in dentifrices, there has been little improvement in the toothbrush used by the vast majority of persons practicing dental hygiene on a two- or three-time a day basis. That is not to say that changes in bristle quality, shape of the brush and/or size of the toothbrush article have not been improvements; but to the average toothbrush user, parametric changes to the conventional, straight handled "scrubbing" toothbrush comprise the preponderance of improvements to the original. Of course, there have been marketed numerous toothbrushes wherein the bristles or brushes of the apparatus move reciprocatively in lateral or longitudinal translation, and even those which possess rotary bristles or brushes. But, almost all of the truly successful products are motor driven. Short of returning to the pristine handbrush, there is a paucity of manually driven toothbrushes in which the bristles are caused to translate or rotate after the fashion of the many power driven brushes, as discussed above.
In making the instant invention, I performed a diligent search, not only on the market shelves and in catalogues, but in the records of the United States Patent and Trademark Office as well. Several patents were located, in the latter search effort, in which various patentees improved both power driven and manually operated toothbrushes in order to acquire certain characteristics and/or achieve specific goals. In the former category, power driven brushes, U.S. Pat. No. 4,079,517 issued to Zacharia discloses an electrically driven brush having an extension shaft from the end of which projects an orthogonally disposed rotary brush. Because the brush is electrically powered, Zacharia is particularly concerned with providing water tight seals in the power unit-extension shaft region and at the power unit-rotating shaft interface portion of the unit. A disadvantage of the '517 device is that, even were it not to require (as it does in this case) a transformer unit, the entire ensemble remains both bulky and relatively heavy; and it does not appear to be the type of device which one will readily carry to work and employ regularly away from the home or in the workplace. Although having the advantage of applying uniform force to the teeth and all areas of the mouth, the disadvantages, combined with the cost of production, make this device generally undesirable for usage away from the home. Only a manually operated (driven) and inexpensive device will overcome these disadvantages. In 1981, a power driven brush assembly was patented by Cohen, U.S. Pat. No. 4,274,173, and employed a triple rotary brush ensemble in the cleaning head. The triple rotary brushes are belt driven and therefore move unidirectionally. The main thrust of the '173 teaching appears to be in the cup-shaped cavities located in a free end of each individual brush. Further, the captured brush end appears to be removable from a rotary base which comprises a spur gear. The spur gear bases, however, are toothed in order to engage a drive belt and do not enmesh with each other. Further, a drive pin is used to fixedly secure the brush end in the spur gear base. In addition to having disadvantages which I have cited regarding the '517 device, the '173 employs a drive belt which, if broken, is not easily replaceable by the user. Further, although the patentee means to say that adjacent brush surfaces rotate in opposite directions, the brushes, nonetheless, rotate in the same direction. My studies have convinced me that there is no particular merit to this type of brush movement and, further, obtainment of such is usually at a cost of greater complexity than is either necessary or desired in the multiple brush ensemble. I prefer, as the reader will hereinafter see, to employ a plurality of contrarotating brushes because the scrubbing action is not diminished and the mechanization required for obtaining this function is less costly and far less contrived.
Final to my search of the patent records, a rotary toothbrush disclosed in U.S. Pat. No. 1,949,241, issued to Carlson et al., although encumbered by a thumb actuated rack and drive pinion design, is nonetheless noteworthy for its early genesis and unusual brush shape. Patent '241 employs a transversely mounted, thumb actuated, spring biased rack-on-plunger to engage a pinion gear compounded with a crown/spur gear. The crown gear (of the spur) engages a pinion mounted at the end of a drive shaft. At the other end of the drive shaft is a removably mounted helical brush. The thumb actuated, transversely mounted drive rack plunger has an inherently serious disadvantage. When the '241 brush is held in the hand and the thumb placed on the plunger and actuated to reciprocatively move the rack in a direction transverse the longitudinal axis of the brush, a force coexists which not only serves to rotate the helical brush but also causes a forcing of the brush head end away from the user's teeth. As the spring biased rack/plunger is rebiased, a natural tendency for the user would be to repress the brush onto the surface of the teeth. Thus, in the sporadic pumping action required to actuate the brush, the user inadvertently applies an irregular pressure, almost periodically, to the teeth. Because the thumb actuated rack is subject to a rebiasing mode, a strong deceleration is applied to the brush surface by contact with the teeth and the effects of the rebiasing mechanism then tend to be overridden. To correct this deficiency, a heavier rebiasing spring would only cause the user to apply more pressure to the thumb actuated rack-plunger and thus a greater force when "pushing" the brush off the teeth as (previously) mentioned. It would appear that in '241, actuation transverse the longitudinal axis of the brush is ill-advised in my judgement.
In order to provide a truly functional, portable and manually operable rotary brush device, improvements had to be directed toward certain disadvantages of the current art as well as those factors which encourage regular use of a mechanical contrivance in favor of the more conventional static toothbrushes of the genre.